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Li L, Zhou Y, Wang G, Liao S, Ke Y, Wu W, Li X, Zhang R, Fu Y. Anaphase-promoting complex/cyclosome controls HEC1 stability. Cell Prolif 2011; 44:1-9. [PMID: 21199005 PMCID: PMC6496518 DOI: 10.1111/j.1365-2184.2010.00712.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2010] [Accepted: 06/15/2010] [Indexed: 02/05/2023] Open
Abstract
OBJECTIVE Chromosome segregation during mitosis requires a physically large proteinaceous structure called the kinetochore to generate attachments between chromosomal DNA and spindle microtubules. It is essential for kinetochore components to be carefully regulated to guarantee successful cell division. Depletion, mutation or dysregulation of kinetochore proteins results in mitotic arrest and/or cell death. HEC1 (high expression in cancer) has been reported to be a kinetochore protein, depletion of which, by RNA interference, results in catastrophic mitotic exit. MATERIALS AND METHODS AND RESULTS To investigate how HEC1 protein is controlled post-translation, we analysed the role of anaphase-promoting complex/cyclosome (APC/C)-Cdh1 in degradation of HEC1 protein. In this study, we show that HEC1 is an unstable protein and can be targeted by endogenous ubiquitin-proteasome system in HEK293T cells. Results of RNA interference and in vivo ubiquitination assay indicated that HEC1 could be ubiquitinated and degraded by APC/C-hCdh1 E3 ligase. The evolutionally conserved D-box at the C-terminus functioned as the degron of HEC1, destruction of which resulted in resistance to degradation mediated by APC/C-Cdh1. Overexpression of non-degradable HEC1 (D-box destroyed) induced accumulation of cyclin B protein in vivo and triggered mitotic arrest. CONCLUSION APC/C-Cdh1 controls stability of HEC1, ensuring normal cell cycle progression.
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Affiliation(s)
- L. Li
- Laboratory of Cell Senescence, Shantou University Medical College, Shantou, Guangdong, China
- Department of Molecular Biology; Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong, China
| | - Y. Zhou
- Department of Orthopaedics, the First Affiliated Hospital of PLA General Hospital, Beijing, China
| | - G.‐F. Wang
- Department of Microbiology and Immunology, Shantou University Medical College, Shantou, Guangdong, China
| | - S.‐C. Liao
- Department of Molecular Biology; Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong, China
| | - Y.‐B. Ke
- Department of Molecular Biology; Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong, China
| | - W. Wu
- Department of Molecular Biology; Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong, China
| | - X.‐H. Li
- Department of Molecular Biology; Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong, China
| | - R.‐L. Zhang
- Department of Molecular Biology; Shenzhen Municipal Center for Disease Control and Prevention, Shenzhen, Guangdong, China
| | - Y.‐C. Fu
- Laboratory of Cell Senescence, Shantou University Medical College, Shantou, Guangdong, China
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Montpetit B, Hazbun TR, Fields S, Hieter P. Sumoylation of the budding yeast kinetochore protein Ndc10 is required for Ndc10 spindle localization and regulation of anaphase spindle elongation. ACTA ACUST UNITED AC 2006; 174:653-63. [PMID: 16923829 PMCID: PMC2064309 DOI: 10.1083/jcb.200605019] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Posttranslational modification by the ubiquitin-like protein SUMO (small ubiquitin-like modifier) is emerging as an important regulator in many cellular processes, including genome integrity. In this study, we show that the kinetochore proteins Ndc10, Bir1, Ndc80, and Cep3, which mediate the attachment of chromosomes to spindle microtubules, are sumoylated substrates in budding yeast. Furthermore, we show that Ndc10, Bir1, and Cep3 but not Ndc80 are desumoylated upon exposure to nocodazole, highlighting the possibility of distinct roles for sumoylation in modulating kinetochore protein function and of a potential link between the sumoylation of kinetochore proteins and mitotic checkpoint function. We find that lysine to arginine mutations that eliminate the sumoylation of Ndc10 cause chromosome instability, mislocalization of Ndc10 from the mitotic spindle, abnormal anaphase spindles, and a loss of Bir1 sumoylation. These data suggest that sumoylation of Ndc10 and other kinetochore proteins play a critical role during the mitotic process.
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Affiliation(s)
- Ben Montpetit
- Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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4
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Abstract
The human pathogenic yeast Candida glabrata is the second most common Candida pathogen after Candida albicans, causing both bloodstream and mucosal infections. The centromere (CEN) DNA of C. glabrata (CgCEN), although structurally very similar to that of Saccharomyces cerevisiae, is not functional in S. cerevisiae. To further examine the structure of the C. glabrata inner kinetochore, we isolated several C. glabrata homologs of S. cerevisiae inner kinetochore protein genes, namely, genes for components of the CBF3 complex (Ndc10p, Cep3p, and Ctf13p) and genes for the proteins Mif2p and Cse4p. The amino acid sequence identities of these proteins were 32 to 49% relative to S. cerevisiae. CgNDC10, CgCEP3, and CgCTF13 are required for growth in C. glabrata and are specifically found at CgCEN, as demonstrated by chromatin immunoprecipitation experiments. Cross-complementation experiments revealed that the isolated genes, with the exception of CgCSE4, are species specific and cannot functionally substitute for the corresponding genes in S. cerevisiae deletion strains. Likewise, the S. cerevisiae CBF3 genes NDC10, CEP3, and CTF13 cannot functionally replace their homologs in C. glabrata CBF3 deletion strains. Two-hybrid analysis revealed several interactions between these proteins, all of which were previously reported for the inner kinetochore proteins of S. cerevisiae. Our findings indicate that although many of the inner kinetochore components have evolved considerably between the two closely related species, the organization of the C. glabrata inner kinetochore is similar to that in S. cerevisiae.
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Affiliation(s)
- Tanja Stoyan
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.
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5
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Ulrich HD. Degradation or maintenance: actions of the ubiquitin system on eukaryotic chromatin. EUKARYOTIC CELL 2002; 1:1-10. [PMID: 12455966 PMCID: PMC118055 DOI: 10.1128/ec.1.1.1-10.2002] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Helle D Ulrich
- Max Planck Institute for Terrestrial Microbiology, D-35043 Marburg, Germany.
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6
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Usuba T, Ishibashi Y, Okawa Y, Hirakawa T, Takada K, Ohkawa K. Purification and identification of monoubiquitin-phosphoglycerate mutase B complex from human colorectal cancer tissues. Int J Cancer 2001; 94:662-8. [PMID: 11745460 DOI: 10.1002/ijc.1524] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ubiquitin-conjugated proteins in human colorectal cancer tissues were analyzed by the immunoprecipitation with the antibody FK2 against conjugated ubiquitin followed with SDS-PAGE. In these immunoprecipitable proteins, a 38-kDa protein was abundant in the tumor regions but almost absent in the adjacent normal regions in 17/26 patients, thus we attempted to purify it. Using immunoaffinity chromatography with the antibody FK2 followed by gel filtration and SDS-PAGE, approximately 10 pmol of this protein was separated from 34 g of the pooled cancerous tissue and transferred onto a PVDF membrane. The 38-kDa protein was further digested with Achromobacter protease I, resulting in several peptide fragments. Amino acid sequences of these peptides showed complete sequence identity to those derived from either ubiquitin or phosphoglycerate mutase-B, suggesting that the 38-kDa protein is monoubiquitinated phosphoglycerate mutase-B, whose calculated mass is 37,369 Da. Western blot using an antibody against phosphoglycerate mutase-B revealed the presence of the 38-kDa protein in the anti-ubiquitin immunoprecipitates derived from the tumor regions, but not from normal counterparts. In addition, part of non-ubiquitinated phosphoglycerate mutase-B (29 kDa) was also found in the anti-ubiquitin immunoprecipitates, whose levels were higher in the tumor regions than in the adjacent normal regions. These results suggest that monoubiquitination of phosphoglycerate mutase-B as well as formation of a noncovalent complex containing ubiquitin and phosphoglycerate mutase-B increases in colorectal cancer and novel modification of phosphoglycerate mutase-B might have a pathophysiological role.
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Affiliation(s)
- T Usuba
- Department of Surgery, Jikei University School of Medicine, Nishishinbashi, Minato-ku, Tokyo, Japan
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7
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Topper LM, Bastians H, Ruderman JV, Gorbsky GJ. Elevating the level of Cdc34/Ubc3 ubiquitin-conjugating enzyme in mitosis inhibits association of CENP-E with kinetochores and blocks the metaphase alignment of chromosomes. J Cell Biol 2001; 154:707-17. [PMID: 11514588 PMCID: PMC2196447 DOI: 10.1083/jcb.200104130] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cdc34/Ubc3 is a ubiquitin-conjugating enzyme that functions in targeting proteins for proteasome-mediated degradation at the G1 to S cell cycle transition. Elevation of Cdc34 protein levels by microinjection of bacterially expressed Cdc34 into mammalian cells at prophase inhibited chromosome congression to the metaphase plate with many chromosomes remaining near the spindle poles. Chromosome condensation and nuclear envelope breakdown occurred normally, and chromosomes showed oscillatory movements along mitotic spindle microtubules. Most injected cells arrested in a prometaphase-like state. Kinetochores, even those of chromosomes that failed to congress, possessed the normal trilaminar plate ultrastructure. The elevation of Cdc34 protein levels in early mitosis selectively blocked centromere protein E (CENP-E), a mitotic kinesin, from associating with kinetochores. Other proteins, including two CENP-E-associated proteins, BubR1 and phospho-p42/p44 mitogen-activated protein kinase, and mitotic centromere-associated kinesin, cytoplasmic dynein, Cdc20, and Mad2, all exhibited normal localization to kinetochores. Proteasome inhibitors did not affect the prometaphase arrest induced by Cdc34 injection. These studies suggest that CENP-E targeting to kinetochores is regulated by ubiquitylation not involving proteasome-mediated degradation.
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Affiliation(s)
- L M Topper
- Department of Cell Biology, University of Virginia, Charlottesville, VA 22908, USA
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8
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Hemmerich P, Stoyan T, Wieland G, Koch M, Lechner J, Diekmann S. Interaction of yeast kinetochore proteins with centromere-protein/transcription factor Cbf1. Proc Natl Acad Sci U S A 2000; 97:12583-8. [PMID: 11070082 PMCID: PMC18807 DOI: 10.1073/pnas.97.23.12583] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The centromere-kinetochore complex of Saccharomyces cerevisiae is a specialized chromosomal substructure that mediates attachment of duplicated chromosomes to the mitotic spindle by a regulated network of protein-DNA and protein-protein interactions. We have used in vitro assays to analyze putative molecular interactions between components of the yeast centromerekinetochore complex. Glutathione S-transferase pull-down experiments showed the direct interaction of in vitro translated p110, p64, and p58 of the essential CBF3 kinetochore protein complex with Cbf1p, a basic region helix-loop-helix zipper protein (bHLHzip) that specifically binds to the CDEI region on the centromere DNA. Furthermore, recombinant p64 and p23 each stimulated the in vitro DNA binding activity of Cbf1p. The N-terminal 70 amino acids of p23 were sufficient to mediate this effect. P64 could also promote the multimerization activity of Cbf1p in the presence of centromere DNA in vitro. These results show the direct physical interaction of Cbf1p and CBF3 subunits and provide evidence that CBF3 components can promote the binding of Cbf1p to its binding site in the yeast kinetochore. A functional comparison of the centromere binding proteins with transcription factors binding at MET16 promoters reveals the strong analogy between centromeres and the MET16 promoter.
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Affiliation(s)
- P Hemmerich
- Institut fuer Molekulare Biotechnologie, Abteilung Molekularbiologie, Beutenbergstrasse 11, 07745 Jena, Germany.
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9
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Kaiser P, Flick K, Wittenberg C, Reed SI. Regulation of transcription by ubiquitination without proteolysis: Cdc34/SCF(Met30)-mediated inactivation of the transcription factor Met4. Cell 2000; 102:303-14. [PMID: 10975521 DOI: 10.1016/s0092-8674(00)00036-2] [Citation(s) in RCA: 249] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Polyubiquitination of proteins by Cdc34/SCF complexes targets them for degradation by the 26S proteasome. The essential F-box protein Met30 is the substrate recognition subunit of the ubiquitin ligase SCF(Met30). The critical target of SCF(Met30) is the transcription factor Met4, as deletion of MET4 suppresses the lethality of met30 mutants. Surprisingly, Met4 is a relatively stable protein and its abundance is not influenced by Met30. However, transcriptional repression of Met4 target genes correlates with Cdc34/SCF(Met30)-dependent ubiquitination of Met4. Functionally, ubiquitinated Met4 associates with target promoters but fails to form functional transcription complexes. Our data reveal a novel proteolysis-independent function for Cdc34/SCF and indicate that ubiquitination of transcription factors can be utilized to directly regulate their activities.
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Affiliation(s)
- P Kaiser
- The Scripps Research Institute, MB7, La Jolla, California, USA
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10
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Bastians H, Topper LM, Gorbsky GL, Ruderman JV. Cell cycle-regulated proteolysis of mitotic target proteins. Mol Biol Cell 1999; 10:3927-41. [PMID: 10564281 PMCID: PMC25689 DOI: 10.1091/mbc.10.11.3927] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/1999] [Accepted: 08/24/1999] [Indexed: 11/11/2022] Open
Abstract
The ubiquitin-dependent proteolysis of mitotic cyclin B, which is catalyzed by the anaphase-promoting complex/cyclosome (APC/C) and ubiquitin-conjugating enzyme H10 (UbcH10), begins around the time of the metaphase-anaphase transition and continues through G1 phase of the next cell cycle. We have used cell-free systems from mammalian somatic cells collected at different cell cycle stages (G0, G1, S, G2, and M) to investigate the regulated degradation of four targets of the mitotic destruction machinery: cyclins A and B, geminin H (an inhibitor of S phase identified in Xenopus), and Cut2p (an inhibitor of anaphase onset identified in fission yeast). All four are degraded by G1 extracts but not by extracts of S phase cells. Maintenance of destruction during G1 requires the activity of a PP2A-like phosphatase. Destruction of each target is dependent on the presence of an N-terminal destruction box motif, is accelerated by additional wild-type UbcH10 and is blocked by dominant negative UbcH10. Destruction of each is terminated by a dominant activity that appears in nuclei near the start of S phase. Previous work indicates that the APC/C-dependent destruction of anaphase inhibitors is activated after chromosome alignment at the metaphase plate. In support of this, we show that addition of dominant negative UbcH10 to G1 extracts blocks destruction of the yeast anaphase inhibitor Cut2p in vitro, and injection of dominant negative UbcH10 blocks anaphase onset in vivo. Finally, we report that injection of dominant negative Ubc3/Cdc34, whose role in G1-S control is well established and has been implicated in kinetochore function during mitosis in yeast, dramatically interferes with congression of chromosomes to the metaphase plate. These results demonstrate that the regulated ubiquitination and destruction of critical mitotic proteins is highly conserved from yeast to humans.
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Affiliation(s)
- H Bastians
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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11
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Kitagawa K, Skowyra D, Elledge SJ, Harper JW, Hieter P. SGT1 encodes an essential component of the yeast kinetochore assembly pathway and a novel subunit of the SCF ubiquitin ligase complex. Mol Cell 1999; 4:21-33. [PMID: 10445024 DOI: 10.1016/s1097-2765(00)80184-7] [Citation(s) in RCA: 276] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We have identified SGT1 as a dosage suppressor of skp1-4, a mutation causing defects in yeast kinetochore function. Sgt1p physically associates with Skp1p in vivo and in vitro. SGT1 is an essential gene, and different sgt1 conditional mutants arrest with either a G1 or G2 DNA content. Genetic and phenotypic analyses of sgt1-3 (G2 allele) mutants support an essential role in kinetochore function. Sgt1p is required for assembling the yeast kinetochore complex, CBF3, via activation of Ctf13p. Sgt1p also associates with SCF (Skp1p/Cdc53p/F box protein) ubiquitin ligase. sgt1-5 (G1 allele) mutants are defective in Sic1p turnover in vivo and Cln1p ubiquitination in vitro. Human SGT1 rescues an sgt1 null mutation, suggesting that the function of SGT1 is conserved in evolution.
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Affiliation(s)
- K Kitagawa
- Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
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12
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Skibbens RV, Hieter P. Kinetochores and the checkpoint mechanism that monitors for defects in the chromosome segregation machinery. Annu Rev Genet 1999; 32:307-37. [PMID: 9928483 DOI: 10.1146/annurev.genet.32.1.307] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Whether we consider the division of the simplest unicellular organisms into two daughter cells or the generation of haploid gametes by the most complex eukaryotes, no two processes secure the continuance of life more than the proper replication and segregation of the genetic material. The cell cycle, marked in part by the periodic rise and fall of cyclin-dependent kinase (CDK) activities, is the means by which these two processes are separated. DNA damage and mistakes in chromosome segregation are costly, so nature has further devised elaborate checkpoint mechanisms that halt cell cycle progression, allowing time for repairs or corrections. In this article, we review the mitotic checkpoint mechanism that responds to defects in the chromosome segregation machinery and arrests cells in mitosis prior to anaphase onset. At opposite ends of this pathway are the kinetochore, where many checkpoint proteins reside, and the anaphase-promoting complex (APC), the metaphase-to-interphase transition regulator. Throughout this review we focus on budding yeast but reference parallel processes found in other organisms.
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Affiliation(s)
- R V Skibbens
- Carnegie Institute of Washington, Department of Embryology, Baltimore, Maryland 21210, USA.
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13
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Tavormina PA, Burke DJ. Cell cycle arrest in cdc20 mutants of Saccharomyces cerevisiae is independent of Ndc10p and kinetochore function but requires a subset of spindle checkpoint genes. Genetics 1998; 148:1701-13. [PMID: 9560388 PMCID: PMC1460108 DOI: 10.1093/genetics/148.4.1701] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The spindle checkpoint ensures accurate chromosome segregation by inhibiting anaphase onset in response to altered microtubule function and impaired kinetochore function. In this study, we report that the ability of the anti-microtubule drug nocodazole to inhibit cell cycle progression in Saccharomyces cerevisiae depends on the function of the kinetochore protein encoded by NDC10. We examined the role of the spindle checkpoint in the arrest in cdc20 mutants that arrest prior to anaphase with an aberrant spindle. The arrest in cdc20 defective cells is dependent on the BUB2 checkpoint and independent of the BUB1, BUB3, and MAD spindle checkpoint genes. We show that the lesion recognized by Bub2p is not excess microtubules, and the cdc20 arrest is independent of kinetochore function. We show that Cdc20p is not required for cyclin proteolysis at two points in the cell cycle, suggesting that CDC20 is distinct from genes encoding integral proteins of the anaphase promoting complex.
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Affiliation(s)
- P A Tavormina
- Department of Biology, University of Virginia, Charlottesville 22903, USA
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14
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Winkler AA, Bobok A, Zonneveld BJ, Steensma HY, Hooykaas PJ. The lysine-rich C-terminal repeats of the centromere-binding factor 5 (Cbf5) of Kluyveromyces lactis are not essential for function. Yeast 1998; 14:37-48. [PMID: 9483794 DOI: 10.1002/(sici)1097-0061(19980115)14:1<37::aid-yea198>3.0.co;2-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The gene coding for the centromere-binding factor 5 (CBF5) of Kluyveromyces lactis has been isolated by hybridization of a Saccharomyces cerevisiae CBF5 DNA probe to a K. lactis library. The amino acid sequence of KlCbf5 is highly homologous, 88% identity, to ScCbf5, but also to the rat protein Nap57 (64% identity). The main difference between both yeast proteins and the rat protein is the presence of a lysine-rich domain with KKE/D repeats in the C-terminal part of the protein. These repeats are thought to be involved in binding of the protein to microtubules. Deletion of the KKE/D domain in KlCbf5 however, has no discernible effect on growth on rich medium, sensitivity to the microtubule-destabilizing drug benomyl or segregation of a reporter plasmid. On the other hand, insertion of two leucine residues adjacent to the KKE domain increases the loss rate of a reporter plasmid. In both yeasts complementation of a lethal CBF5 disruption with the heterologous gene results in a slight increase in benomyl sensitivity. A possible role of CBF5 in chromosome segregation will be discussed.
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Affiliation(s)
- A A Winkler
- Institute for Molecular Plant Sciences, Leiden, The Netherlands
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15
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16
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Kopski KM, Huffaker TC. Suppressors of the ndc10-2 mutation: a role for the ubiquitin system in Saccharomyces cerevisiae kinetochore function. Genetics 1997; 147:409-20. [PMID: 9335582 PMCID: PMC1208167 DOI: 10.1093/genetics/147.2.409] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We have isolated a new conditional-lethal mutation, ndc10-2, in the NDC10/CBF2/CTF14 gene that encodes the 110-kD subunit of the Saccharomyces cerevisiae CBF3 kinetochore complex. At the restrictive temperature of 37 degrees, ndc10-2 cells are able to assemble anaphase spindles, but fail to segregate their DNA, consistent with a defect in kinetochore function. To identify other factors that play a role in kinetochore assembly or function, we isolated both dosage and second site suppressors of the ndc10-2 mutation. These screens identified UBC6 as a dosage suppressor, and mutations in UBC6 and UBC7 as second-site suppressors of ndc10-2 heat sensitivity. Both UBC6 and UBC7 encode ubiquitin-conjugating enzymes that function in ubiquitin-mediated protein degradation. Furthermore, overexpression of a mutant ubiquitin suppresses the ndc10-2 mutation. These results implicate the ubiquitin system in the regulation of ndc10-2 function and suggest a role for the ubiquitin system in kinetochore function.
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Affiliation(s)
- K M Kopski
- Section of Biochemistry, Molecular and Cellular Biology, Cornell University, Ithaca, New York 14853-2703, USA
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17
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Abstract
An emerging view is that the formation of active centromeres is modulated in an epigenetic manner reflecting the association of centromeres with heterochromatin. Support for this comes from studies on fission yeast centromeres, the properties of human neocentromeres and dicentric chromosomes, and analyses of Drosophila minichromosome deletion derivatives. A link has been established between tension across kinetochores and the phosphorylation status of kinetochore components. Vertebrate homologues of yeast MAD2 have recently been isolated and localized to kinetochores, indicating that components of the spindle integrity checkpoint are conserved. The linkage between sister chromatids is only dissolved at anaphase during mitotic and meiotic divisions. Phenotypic and localization data combined with their pattern of rapid degradation at anaphase have implicated several yeast and Drosophila proteins in aspects of sister chromatid cohesion.
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Affiliation(s)
- R C Allshire
- MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK.
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18
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Deshaies RJ. Phosphorylation and proteolysis: partners in the regulation of cell division in budding yeast. Curr Opin Genet Dev 1997; 7:7-16. [PMID: 9024629 DOI: 10.1016/s0959-437x(97)80103-7] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The budding yeast cell cycle oscillates between states of low and high cyclin B/cyclin-dependent kinase (CLB/CDK) activity. Remarkably, the two transitions that link these states are governed by ubiquitin-mediated proteolysis. The transition from low to high CLB activity is triggered by degradation of the CLB/CDK inhibitor SIC1, and the complementary excursion is propelled by the proteolytic destruction of CLBs. The extracellular environment controls this two-state circuit by regulating G1 cyclin/CDK activity, which is directly required for SIC1 proteolysis. Thus, stable oscillations of chromosome replication and segregation in budding yeast are propagated by the interplay between protein phosphorylation and protein degradation.
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Affiliation(s)
- R J Deshaies
- Division of Biology, California Institute of Technology, Pasadena California, 91125 USA.
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19
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Willems AR, Lanker S, Patton EE, Craig KL, Nason TF, Mathias N, Kobayashi R, Wittenberg C, Tyers M. Cdc53 targets phosphorylated G1 cyclins for degradation by the ubiquitin proteolytic pathway. Cell 1996; 86:453-63. [PMID: 8756727 DOI: 10.1016/s0092-8674(00)80118-x] [Citation(s) in RCA: 256] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In budding yeast, cell division is initiated in late G1 phase once the Cdc28 cyclin-dependent kinase is activated by the G1 cyclins Cln1, Cln2, and Cln3. The extreme instability of the Cln proteins couples environmental signals, which regulate Cln synthesis, to cell division. We isolated Cdc53 as a Cln2-associated protein and show that Cdc53 is required for Cln2 instability and ubiquitination in vivo. The Cln2-Cdc53 interaction, Cln2 ubiquitination, and Cln2 instability all depend on phosphorylation of Cln2. Cdc53 also binds the E2 ubiquitin-conjugating enzyme, Cdc34. These findings suggest that Cdc53 is a component of a ubiquitin-protein ligase complex that targets phosphorylated G1 cyclins for degradation by the ubiquitin-proteasome pathway.
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Affiliation(s)
- A R Willems
- Programme in Molecular Biology and Cancer Samuel Lunenfeld Research Institute Mount Sinai Hospital, Toronto, Canada
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20
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Stemmann O, Lechner J. The Saccharomyces cerevisiae kinetochore contains a cyclin-CDK complexing homologue, as identified by in vitro reconstitution. EMBO J 1996; 15:3611-20. [PMID: 8670864 PMCID: PMC451974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We have developed methods to reconstitute the centromere DNA (CEN)-bound Saccharomyces cerevisiae kinetochore complex, CBF3, from isolated CBF3 components in vitro. This revealed that cooperation of at least three CBF3 components is imperatively required to form an activity that specifically binds to the centromere DNA in vitro. Two of the CBF3 proteins, Cbf3a and Cbf3b, that were used in the reconstitution were obtained from heterologous systems. In contrast, Cbf3c, the third CBF3 component known, had to be purified from S. cerevisiae to obtain a Cbf3c preparation that was competent to reconstitute the CBF3-CEN complex in combination with Cbf3a and Cbf3b. This led to the identification of a 29 kDa protein that co-purified with Cbf3c. The 29 kDa protein was shown to be a fourth component of CBF3 and therefore was named Cbf3d. Analysing the Cbf3d gene revealed that Cbf3d exhibits strong homology to p19SKP1, a human protein that is part of active cyclin A-CDK2 complexes. Therefore, Cbf3d is the only CBF3 protein that has a known homologue in higher eukaryotes and may provide the anchor that directs cell cycle-regulated proteins to the kinetochore.
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Affiliation(s)
- O Stemmann
- Institut für Biochemie, Universität Regensburg, Germany
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Abstract
Accurate chromosome segregation is dependent on a specialized chromosomal structure, the kinetochore/centromere. The only essential constituent of the S. cerevisiae kinetochore established today is CBF3, a multisubunit complex that binds to S. cerevisiae centromere DNA. Therefore CBF3 and its four components, Cbf3a, Cbf3b, Cbf3c and Cbf3d, will form the centerpiece of this review. In addition, we will describe proteins that are putatively involved in kinetochore function specifically in the context with CBF3 interaction. Furthermore, we discuss the role of the S. cerevisiae kinetochores in a putative cell cycle checkpoint control and in microtubule attachment.
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Affiliation(s)
- J Lechner
- Institut für Biochemie, Genetik und Mikrobiologie, Universität Regensburg, Germany.
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Jiang W, Koltin Y. Two-hybrid interaction of a human UBC9 homolog with centromere proteins of Saccharomyces cerevisiae. MOLECULAR & GENERAL GENETICS : MGG 1996; 251:153-60. [PMID: 8668125 DOI: 10.1007/bf02172913] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using a two-hybrid system, we cloned a human cDNA encoding a ubiquitin-conjugating enzyme (UBC), hUBC9, which interacts specifically with all three subunits of the Saccharomyces cerevisiae centromere DNA-binding core complex, CBF3. The hUBC9 protein shows highest homology to a new member of the UBC family: 54% identity to S. cerevisiae Ubc9p and 64% identity to Schizosaccharomyces pombe (Sp) hus5. Overexpression of hUBC9 partially suppresses a S. cerevisiae ubc9 temperature-sensitive mutation, indicating that the UBC9 gene family is also functionally conserved. Like hUBC9, Sphus5 also interacts specifically with all three subunits of the CBF3 complex. However, S. cerevisiae Ubc9p interacts only with the Cbf3p subunit (64 kDa) of the CBF3 complex, indicating the specificity of the interaction between S. cerevisiae Ubc9 and Cbf3p proteins. The function of Ubc9p in the G2/M phase of S. cerevisiae could be related to regulation of centromere proteins in chromosome segregation in mitosis. Therefore, the ubiquitination process and centromere function may be linked to chromosome segregation. We also provide further in vivo evidence that Mck1p, a protein kinase, is specifically associated with the centromere proteins Cbf2p and Cbf5p, which were previously shown to interact in vitro.
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Affiliation(s)
- W Jiang
- Myco Pharmaceuticals Inc., Cambridge, MA 02139, USA
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Kovalenko OV, Plug AW, Haaf T, Gonda DK, Ashley T, Ward DC, Radding CM, Golub EI. Mammalian ubiquitin-conjugating enzyme Ubc9 interacts with Rad51 recombination protein and localizes in synaptonemal complexes. Proc Natl Acad Sci U S A 1996; 93:2958-63. [PMID: 8610150 PMCID: PMC39742 DOI: 10.1073/pnas.93.7.2958] [Citation(s) in RCA: 137] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Hsubc9, a human gene encoding a ubiquitin-conjugating enzyme, has been cloned. The 18-kDa HsUbc9 protein is homologous to the ubiquitin-conjugating enzymes Hus5 of Schizosaccharomyces pombe and Ubc9 of Saccharomyces cerevisiae. The Hsubc9 gene complements a ubc9 mutation of S. cerevisiae. It has been mapped to chromosome 16p13.3 and is expressed in many human tissues, with the highest levels in testis and thymus. According to the Ga14 two-hybrid system analysis, HsUbc9 protein interacts with human recombination protein Rad51. A mouse homolog, Mmubc9, encodes an amino acid sequence that is identical to the human protein. In mouse spermatocytes, MmUbc9 protein, like Rad51 protein, localizes in synaptonemal complexes, which suggests that Ubc9 protein plays a regulatory role in meiosis.
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Affiliation(s)
- O V Kovalenko
- Department of Genetics, Yale University School of Medicine, New Haven CT 06510, USA
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